Methods and apparatus for bending tubes



Aug. 4, 1959' A. HUET METHODS AND APPARATUS FOR BENDING TUBES Filed June15. 1956 as arm/1401111000118 Fig. 2

United States Patent METHODS AND APPARATUS FOR BENDING TUBES Andre Huet,Paris, France Application June 13, 1956, Serial No. 591,132

1 Claim. Cl. 153-48) This invention relates to a method of bending tubesconsiderable time and in addition time is needed to in-' sert the tubein the bending machine; as a result, either by conduction or radiation,the heat distributes itself over the whole periphery of the tube insteadof, as is intended, acting on a specific region only.

The present invention provides a method and a device which enable thedesired difierential temperatures, to be maintained between the variousregions of the tube to ensure perfect bending.

According to the present invention a method of bending a tube whereinthe conservation of the differential temperatures to be maintained inthe tube subjected to a bending operation involving the generation ofdifierential temperatures in certain regions of the tube, and moreespecially of a higher temperature in that region of the tube which willeventually form the inside bend of the elbow, is ensured by theprovision, inside the tube in a resilient filling material, such assand, of means for coolng, for example by moistening, the fillingmaterial in that tube region or those tube regions which is or are to beheated to a lower temperature than the remainder of the tube.

The present invention also provides apparatus for the performance of themethod of invention which comprises a preferably semi-flexible,perforated tube through which water flows, said perforated tube beinginserted in the tube to be bent.

The apparatus may also include a strip of preferably flexible sheetmetal so shaped that it can likewise be inserted in the tube to be bentfor the purpose of forming a partition between two zones of fillingsand.

The present invention will now be described in greater detail, by way ofexample only, with reference to the accompanying drawing, of which,

Fig. 1 shows a cross-section through a tube in which the filling deviceof the invention has. been inserted, and

Fig. 2 shows a longitudinal section through the tube region undertreatment, lodged in the bending die.

If it is desired to bend, for example, the tube region a, the tube isfirst filled with sand b and, if desired, the ends of the tube areclosed by means of stoppers c 0 (Fig. 2). Thus, when the ends of thetube are not closed by stoppers c and c cooling water can freely escapeand, by loosely fitting the stoppers when used, an escape route for thecooled water can be similarly provided. Alternatively, if it is desiredto insert the stoppers c and c tightly, these stoppers are convenientlyprovided with at least one peripheral groove as shown at i and i in Fig.2.

In performing the afore-mentioned bending method, the tube region AB ofthe tube a--which eventually becomes the inside bend of the elbow-isheated to a temperature greater than that of the region CD whicheventually becomes the outside bend of the elbow.

In the sand b in the lower half of the tube there is inserted apreferably semi-flexible, perforated tube d through which flows acooling means, such as pressurised water, which moistens the sand b inthe region CD. The perforations in the tube d preferably face that wallportion of the tube a which is to remain colder.

To complete the action of the device there may further be inserted inthe tube a, as shown in Fig. 1, a preferably flexible strip of sheetmetal 2 to separate the sand in region CD from the sand in region AB.

Thus, when the region AB of the tube is heated, the heat is no longer soeasily transmitted by conduction or by radiation to the region CD whichis shielded oif from the heat by the moist sand.

The tube a is then bent by any known method, for instance as representedin Fig. 2 by means of a die h the bottom of which is curved to match thedesired shape of the finished elbow. At the beginning of the bendingwork the tube rests on the two edges of the die 11, and a punch g isapplied to the centre portion of the tube a and exerts pressure in thedirection indicated by the arrow F to press the tube into contact, withthe bottom 1 in the position represented by the chain-dotted lines; thisposition corresponds to a first bending stage. This operation is thenrepeated on successive straight portions of the tube until the tubeforms an elbow matching the curved bottom 1 of the die h. The sand, thetube a, and the metal strip e in the state in which it is after theseoperations, are then withdrawn from the elbow.

Instead of the punch g there may be used a punch extending over thewhole length of the tube a and shaped to match the form of the insidebend of the finished elbow.

As a result of the above described arrangement the heat applied is nottransmitted during the heating operation by conduction or by radiationto the tube region which is to remain colder. When the tube so preparedis then subjected to the bending operation, the finished elbow is ofinfinitely superior quality; more especially, the internalcross-sectional area of the elbow is larger. The bending work as suchmay be carried out in any known manner, either by means of a groovedformer or of a die-and-punch set, that is to say by compressing the tubein a die so curved as to produce the desired final shape.

I claim:

In an apparatus for bending a tube while filled with a body of resilientporous material comprising a die and a punch for shaping the tubetherebetween to define a convex portion and a concave portion, incombination, a perforated tube receivable in the body of the resilientporous filling material contained in said tube on the side of the axisof said tube adjacent said convex portion, said perforated tube beingconnectable to a source of water to conduct water in a plurality ofstreams into direct contact with said filling material, and a flexibleplate receivable axially in said tube within said body of fillingmaterial and dimensioned to intercept the interior surface of said tubealong two axial surface lines to provide a partition therebetween toconfine part of said body to filling material adjacent said concaveportion and to confine the remainder of said body of filling materialad- Patented Aug. 4, 1959 jacent said convex portion of the tube, thesaid remainder of said body receiving said perforated tube.

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